1. Field of the Invention
The present invention relates to novel compounds having anti-hyperlipidemic activity and to processes for their production, and more particularly, is converned with novel triterpenyl esters of organic acids [except triterpenyl esters of ferulic acid (4-hydroxy-3-methoxycinnamic acid) and of monobasic and dibasic saturated fatty acids] having excellent anti-hyperlipidemic activity and low toxicity and with processes for the production of these esters.
The invention further relates to anti-atherosclerotic and hypolipidemic agents which contain the above-mentioned novel compounds and the known compounds (i.e. cycloartenyl, cyclobranyl, and 24-methylenecycloartanyl esters of ferulic acid, or monobasic saturated fatty acids, and cyclobranol).
More specifically, the present invention relates to excellently active and low toxic agents for treatment of hyperlipidemia or hyperlipoproteinemia, that is, safety and novel hypolipidemic and antiatherosclerotic agents which contain triterpenyl esters of organic acids, preferably, cycloartenyl, cyclobranyl, and 24-methylenecycloartanyl esters of organic acids including esters from triterpenyl alcohols and ferulic acid or monobasic saturated C.sub.4 .about.C.sub.20 fatty acids, and cyclobranol alone, as respective active ingredients.
2. Description of the Prior Art
It is well known that hyperlipidemia or hyperlipoproteinemia is one of the most serious factors causing atherosclerosic, a form of arteriosclerosis, especially coronary heart disease. Miller and Miller (G. J. Miller and N. E. Miller, Lancet Jan. 4, p. 16 (1975)) have observed a negative correlation between the concentration of high density lipoprotein choresterol (hereinafter referred to as HDL-C) in blood plasma and the cholesterol pool in the body, and no correlation between either the concentration of total cholesterol (hereinafter referred to as TC) for the concentration of other lipoproteins, and the cholesterol pool, and therefrom proposed the theory that the reduction of cholesterol clearance from the arteries caused by a decrease in the HDL-C concentration in blood promotes arteriosclerosis. Since the proposal of this theory, a number of epidemiological studies (e.g. T. Gordon et al., Am. J. Med., 62. 707 (1977)) have proved the presence of a reverse correlation between the onset of ischemic heart disease and the concentration of HDL-C, and comfirmed that a decrease in the HDL-C concentration in blood is one of the most serious factors causing ischemic heart disease regardless of the presence or absence of an anti-hyperlipidemic agent.
It has so far been known that phytosterols reduce the content of cholesterol in serum. For example, a mixture of .beta.-sitosterol and dihydro-.beta.-sitosterol (supplied by Lilly Co., U.S.A. under the tradename of Cytellin) and a mixture of soysterol, phytosterol, and tocopherol (supplied by Morishita Pharaceutical Co., Ltd. Japan, under the trandename of Moristerol) are on the market as anti-hyperlipedemic agents.
On the other hand, the following is reported on triterpenyl alcohols.
Japanese Patent Application Laid-Open No. 18617/1982 describes that when a phytosterol (1 part) was used jointly with a cycloartenol or 24-methylenecycloartanol (0.01-0.1 part), a stronger action of lowering serum cholesterol than that of phytosterol singly was exhibited by synergism.
Japanese Patent Application Laid-Open No. 116415/1983 also describes that a considerably stronger action depressing serum cholesterol due to synergistic effect was observed in the case of joint use of a phytosterol (100 parts) with cycloartenol, 24-methylencycloartanol, or cyclolandenol (1-20 parts, particularly about 5 parts) than in the case of single use of the phytosterol. In particular, cycloartenol has synergistic effect on the serum cholesterol lowering action of phytosterol, while 24-methylenecycloartanol and cyclolandenol have weaker effect than that of cycloartenol.
Japanese Patent Application Laid-Open No. 27824/1984 reports that when 1% of cycloartenol or 24-methylenecycloartanol was added to a diet containing 0.5% of cholesterol, the respective percentages of TC lowering were 13.7% and 10.2% based on a control with high cholesterol diet (calculated by the present inventors from the data shown in Table 2 of the above patent Laid-Open Gazette).
However, these three patent applications described none of triglyceride (hereinafter referred to as TG), total phospholipid (hereinafter referred to as PL), HDL-C, atherogenic index [(TC - HDL-C)/(HDL-C), hereinafter referred to as AI: some Japanese medical scientists designate the AI as cholesterol ratio or arteriosclerosis index], and lipid peroxide (hereinafter referred to as LPO), though reporting on the action of TC lowering in serum.
From the fact that cycloartenol, 24-methylenecyclo artanol, and cyclolaudenol, alone or in combination with a phytosterol, depressed TC in serum, it is not obvious that these triterpenyl alcohols have also the action of lowering the other items of serum lipids TG, PL, and LPO which are important for treating or diagnosing hyperlipidemic conditions, and that these alcohols have the effect of increasing HDL-C, which is currently considered as particularly significant for treating hyperlipidemia, and in addition the effect of lowering AI. It is impossible to predict such overall pharmacological activity from analogy.
The .gamma.-orizanol on the market today in Japan as a therapeutic agent for treating whiplash syndrome (head or cervical damage) is not composed of a single component but mixtures of various phytosteryl and triterpenyl esters of ferulic acid. An example of the .gamma.-organol is composed of campesteryl (14%), stigmasteryl (1%), .beta.-sitosteryl (4%), cycloartanyl (2%), cycloartenyl (35%), and 24-methylenecycloartonyl (44%) esters of ferulic acid but little cyclobranyl ester of ferulic acid.
Recently the following report on the influence of .gamma.-orizanol upon cholesterol metabolism in hyperlipidemic rats was published by F. Kuzuya et al. (Geriatric Medicine 18, pp 519-524 (1980)). According to the report; TC was explicitly depressed in rats fed with a high cholesterol diet containing 0.1, 0.5, and 1% of .gamma.-orizanol, as compared with TC in control rats fed with the same diet but containing no .gamma.-orizanol, while the degree of the lowering depended on the dosage; the degree of TC lowering was greater than that of PL and comparable to that of HDL-C depression; .gamma.-orizanol showed no activity an AI, but a tendency to increasing TG and the distinct action lowering LPO.
According to K. Mitani et al. [Domyaku Koka, 11, No. 2, June, pp 411-416 (1983)], the serum TC values in rats fed with a high chloresterol diet with 0.5, 1.0, and 2.0% of .gamma.-orizanol were lower by 8.1, 23.4, and 30.9%, respectively, than control rats fed with the same diet but containing no .gamma.-orizanol, while no significant depression was observed in the serum TG and PL values.
According to the study of the influence on hyperlipidemia of hypothalamic obesity rats, by S. Inoue et al. [Domyaku Koka, 11, No. 2, June, pp 417-428 (1983)].gamma.-orizanol exhibited the action of lowering TC but not TG in blood and no effect on PL and HDL-C in blood.
As regards organic acids, R. D. Sharma [Atherosclerosis, 37, pp. 463-468 (1980)] describes; that in rats fed with a high cholesterol diet containing 0.2% of an organic acid, TC level was lowered significantly by 10.8% when the acid was ferulic acid, and by 9.4% when the acid was p-coumaric acid, based on TC level in control rats fed with the same diet but containing none of such organic acids; that the degree of TG level lowering was 18.7% with ferulic acid and 19.8% with p-coumaric acid, but these values were not significant; that the PL level lowering was scarcely observed with both the acids; and that no decrease of TC, TG, or PL level was shown with vanillic acid, caffeic acid, or cinnamic acid.
Although an organic acid was not used singly, the following reports on the anti-hyperlipidemic effect of .alpha.-methylcinnamic acid derivatives was presented. K. Takashima et al. [Biochemical Pharmacology, 27, 2631 (1978)] describe the antihyperlipidemic effect of .alpha.-mono-p-myristyloxy-.alpha.'-methylcinnamoyl glycerol. T. Watanabe et al. [Journal of Medicinal Chemistry, 23, 50 (1980)] describe in detail synthetic methods of p-alkoxycinnamic acids, p-alkoxy-.alpha.-methylcinnamic acids wherein the alkyl moiety in the alkoxy substrituent is 2-propenyl, C.sub.8 -C.sub.18 alkyl, or phenyl; o-, p-, and m- myristyloxycinnamic acids; m-methoxy-p-alkoxy-.alpha.-methylcinnamic acids wherein the alkyl moiety of the alkoxy substituent is C.sub.12 or C.sub.14 alkyl; p-alkoxycinnamates, and p-alkoxyl-.alpha.-methylcinnamates wherein the alkyl moiety of the alkoxy substituent is 2-propenyl, methyl, butyl, or C.sub.8 -C.sub.18 alkyl and the alcohlic residue of the ester is chloroethyl, metharyloxyethyl, monoglyceride residue, diglyceride residue, etc; and anti-hyperlipidemic activities of these compounds. T. Watanabe et al described also a process for producing p-alkoxy-.alpha.-methylcinnamic acids wherein the alkyl moiety of the alkoxy is C.sub.8 -C.sub.16 alkyl) (Japanese Patent Publication No. 45582/1976). T. Ota et al. (Japanese patent application Laid-Open No. 80370/1982) describes .alpha.-methyl-p-pyridyloxycinnamic and .alpha.-methyl-p-pyridylalkyloxycinnamic acids and (C.sub.1 -C.sub.3 alkyl) esters thereof, processes for producing these compounds, and anti-hyperlipidemic compositions containing these compounds.
Recently, Grill, H. et al. [Japanese patent application Laid-Open No. 25953/1985); DE, App. No. 3326164.4 (1983, July, 20)] desribe p-aloxybenzoic acid derivatives such as N-carboxymethyl-4-(2-hydroxy-4-phenylbutoxy) benzamide and 4-[4-(4'-tert-butylphenyl)-2-oxobutoxy] benzoic acid, processes for producing these derivatives, and anti-hyperlipidemic compositions containing these derivatives.
Also, in the past, attempts have been made to lower the levels of cholesterol, phospholipids, an triglycerides in the blood by the oral feeding of various substances which have been generally referred to in the art as hypalipidemic agents or hypocholesteremic adjuvants. Several synthetic hypolipidemic agents are now available, namely, clofibrate, D-thyroxine, cholestyramine, and various nicotinic acid-derivatives.
The development of agents capable of reducing elevated blood lipids and of favorably altering blood-lipoprotein patterns is considered by medical authorities to be extremely important for the treatment and prevention of atherosclerosis.
The present inventors tested the known compounds cycloartenol, 24-methylenecycloartanol, and cyclobranol to ascertain the anti-hyperlipidemic effect thereof. The tests were carried out according to method A (male Wistar strain rats weighing initially 100.+-.1 g were fed for 2 weeks with the diet limited to 10 g/day for each animal but with water given ad libitum) and method B (male Wistar strain rats weighing initially 100.+-.1 g were fed for 4 weeks with the diet and water given ad libitum). Details of these test methods will be described later. Results of these tests shown in Tables 1 and 2 (method A) and Tables 15 and 16 (method B) were as follows: The hypolipidemic effects according to both methods were fundamentally identical. The decrease of TC in serum was observed in the both group given a hyperlipidemic diet containing cycloartenol and given a hyperlipidemic diet containing cyclobranol, at significance levels (P&lt;0.05 according to method A, P&lt;0.01 according to method B), as compared with that in the control group given only a hyperlipidemic diet. The TC lowering due to 24-methylenecycloartanol was slight and not significant according to method A but significant (p&lt;0.05) according to method B). As to HDL-C; cycloartenol depressed it at significant levels (p&lt;0.05 according to method A, p&lt;0.01 according to method B), 24-methylenecycloartanol lowered it slightly with both method so it was not significant. On the contrary, cyclobranol showed a tendency to increasing HDL-C according to both methods though these increases were not significant. Needless to say, HDL-C level is desired to increase significantly, as shown in the foregoing literature.
One of the purposes of the invention is to develop a hypolipidemic agent which significantly lowers TC and increases HDL-C in serum. As stated above, it was confirmed that one of the triterpenyl alcohols, for instance, cycloartanol, cyclobranol, or 24-methylenecycloartanol singly depress TC level in serum significantly. However, no increase in HDL-C content was ascertained in the present inventors' test for hypolipidemic effect according to either methods A or B.
As to AI, cycloartenol and cyclobranol showed tendencies to decrease it according to method A, while 24-methylenecycloartanol showed only a slight tendency to increase. According to method B, the three triterpenyl alcohols showed tendencies to decrease AI. As to TG, PL, and LPO, no significant change was shown with these triterpenyl alcohols according to both methods.
Comparing these three triterpenyl alcohols, cyclobranol tended to lower TC, AI, TG, PL, and LPO but to increase HDL-C, and consequently it was different in the action from cycloartenol and 24-methylenecycloartanol. That is, it has proved that cyclobranol is superior to cycloartenol and 24-methylenecyloartanol in hypolipidemic effect.
Thus, the present inventors have studied aiming at the production of an hypolipidemic agent which will decrease the TC, PL, and TG, contents in serum while the HDL-C content is increased, furthermore an agent which lower AI and LPO contents simultaneously. So our studies have been concentrated on the development of a hypolipidemic agent which has distinctly greater effect in at least 2-3 of 6 items noted above than known triterpenyl alcohols and .gamma.-orizanol. As a result, we discovered a number of novel triterpenyl esters of organic acids having excellent hypolipidemic activity. Further we found that each of the three known triterpenyl esters of ferulic acid, certain esters of monobasic saturated fatty acids, and cyclobranol have high hypolipidemic activity singly. It is difficult to predict these facts from properties of each of the known triterpenyl alcohols, organic acids, and .gamma.-orizanol.